Precipitation cycles in the middle and lower reaches of the Yellow River （1736-2000）

Based on the long-term precipitation series with annual time resolution in the middle and lower reaches of the Yellow River and its four sub-regions during 1736-2000 reconstructed from the rainfall and snowfall archives of the Qing Dynasty, the precipitation cycles are analyzed by wavelet analysis and the possible climate forcings, which drive the precipitation changes, are explored. The results show that： the precipitation in the middle and lower reaches of the Yellow River has inter-annual and inter-decadal oscillations like 2-4a, quasi-22a and 70-80a. The 2-4a cycle is linked with El Nino events, and the precipitation is lower than normal year in the occurrence of the El Nino year or the next year; for the quasi-22a and the 70-80a cycles, Wolf Sun Spot Numbers and Pacific Decadal Oscillation （PDO） coincide with the two cycle signals. However, on a 70-80a time scale, the coincidence between solar activity and precipitation is identified before 1830, and strong （weak） solar activity is generally correlated to the dry （wet） periods; after 1830, the solar activity changes to 80-100a quasi-century long oscillation, and the adjusting action to the precipitation is becoming weaker and weaker; the coincidence between PDO and precipitation is shown in the whole time series. Moreover, in recent 100 years, PDO is becoming a pace-maker of the precipitation on the 70-80a time scale.

Community Structure of the Phytoplankton and Its Relationship with Environmental Factor in Lower Reaches of the Yellow River

[ Objective] The research aimed to study community structure of the phytoplankton and its relationship with environmental factor in lower reaches of the Yellow River. [ Method] From April to June in 2011, phytoplankton was conducted qualitative and quantitative researches in Lijin in lower reaches of the Yellow River. By combining population characteristics of the phytoplankton, its＇relationship with environmental factor was dis- cussed. [ Result] 114 species and 5 phylum of phytoplankton were observed in the whole river section. The abundance of phytoplankton was 0.90 ×104 -303.35×104 ind/m3, and mean was 27.20 ×104 ind/m3. The biomass of phytoplankton was 0.008-5.890 mg/m3, and mean was 0.641 mg/m3. Shannon-Weaver diversity index, Pielou evenness index and Simpson＇s diversity index were respectively 1.59, 0.36 and 0.55. SPSS data analysis indicated that transparency was the uppermost environmental factor affected phytoplankton abundance. Phytoplankton abundance had posi- tive correlation with transparency, and the regression equation was y= -393.8 ＋115.5×-11 .lx2 ＋0.35x3（n=18, R2 =0.952, F=92.665, P〈0.01 ）. [ Conclusion] The community structure of phytoplankton was unstable, and transparency was the uppermost environmental factor affected phyto- plankton abundance in lower reaches of the Yellow River.

The Background of Regional Lead Isotopic Compositions and Its Application in the Lower and Middle Reaches of the Yangtze River and Neighbouring Areas

The paper systematically deals with the background of regional isotopic compo-sitions in the lower and middle reaches of the Yangtze River and neighbouring areas. It isshown that the lead isotopic compositions of different geological formations and units are con-trolled by the primary mantle heterogeneity, dynamic process of crust-mantle interchange,abundances of uraninm, thorium and lead of various layers of the earth and timing. Studies onthe background of regional isotopic compositions may offer significant information forgeochemical regionalization, tracing of sources of ore-forming materials, and regionalprognosis of ore deposits.

Natural Disasters of the Lower Reaches of Yellow River during the Longshan Period——The Natural Background of Dayu's Flood Control

It is very important to study the archaeological culture and origin of civilization in ancient China.The changes of the channels in the lower reaches of the Yellow River in the prehistoric period are part of the natural environmental background of the development of the ancient civilization in that area to be explored.This paper presents a series of legends,indications,scientific evidence,and macroscopic geographical background information of the evolution in the lower reaches of the Yellow River during the Longshan period.At first the river flowed from Northern Henan and Hebei to southwestern Shandong Province and Northern Anhui–Jiangsu provinces,and the mainstream of the Yellow River changed from the southeast to return to the north and flowed into the Bohai Sea in the late Longshan Period.During this period,floods were frequent.Various ethnic groups in the northern China plains suffered natural disasters and made great migrations which also contributed to the ethnic exchanges and integration.The people of the Central Plains made more dynamic adjustments in the relationship between mankind and the land by primitively escaping from the water and self–defensively controlling the rivers then to maintaining the local ecological environment by large–scale flood control measures,which promoted the settlement of Shandong,Henan,Jiangsu and Anhui provinces,the urban cultural development,and social evolution.Based on these events,the culture symbol of Dayu's Flood Control could be formed.

Evaluation of oasis stability in the lower reaches of the Tarim River

Oasis stability in the lower reaches of the Tarim River was assessed at the landscape scale（including changes in landscape pattern and land use in the oasis） and at the regional scale（including the cold-island effect and NDVI of the oasis） based on the methods of landscape ecology,GIS and Remote Sensing（RS）.Thematic Mapping（TM） remote sensing images from 1990,2000 and 2009 were employed along with the related meteorological and hydrological data pertaining to the reclamation area of the oasis in the lower reaches of the Tarim River.The results indicated that landscape heterogeneity and oasis complexity increased between 1990 and 2000.The comprehensive index of the degree of land use,the average index of the cold-island effect,NDVI value and oasis stability all decreased.However,the change trends in the indices referred to above were opposite between 2000 and 2009,and oasis stability was enhanced to some extent.

Water sources of plants and groundwater in typical ecosystems in the lower reaches of the Heihe River Basin

Stable oxygen and hydrogen isotopic compositions （δ18O and δD） of soil water and shallow groundwater of a riparian forest, an artificial shrub forest, and Gobi of the lower reaches of the Heihe River Basin are used to study the recharge water sources of those ecosystems. IsoSource software is used to determine the δ180 values for root water of Populous euphratica and Tamarix ramosissima in the riparian forest ecosystem, Haloxylon ammodendron in the artificial shrub forest, and Reaumuria soongorica in the Gobi, as well as for local soil water and groundwater, and precipitation in the upper reaches of the Heihe River Basin. Our results showed that soil water and shallow groundwater of the riparian forest and the artificial shrub forest were recharged by river water which originated from precipitation in the upper reaches, and strong evaporation occurred in the artificial shrub forest. Soil water of the Gobi was not affected by Heihe River water due to this area being far away from the river channel. The main water sources of Populous euphratica were from 40-60-cm soil water and groundwater, and of Tamarix ramosissima were from 40-80-cm soil water in the riparian forest ecosystem. In the artificial forest, Haloxylon ammodendron used 200-cm saturated-layer soil water and shallow groundwater. The Reaumuria soongorica mainly used soil water from the 175-200-cm depth in the Gobi. Therefore, soil water and groundwater are the main water sources which maintain survival and growth of the plants in the extremely arid regions of the lower reaches of the Heihe River Basin.

Water Environmental Degradation of the Source Area of the Yellow River on Northeast Qinghai-Tibet Plateau

The issue on water environmental degradation in the source area of the Yellow River has been one of very serious ecological and socially economic problems. The temporal-spatial changes of water environment led to the decreasing of land capacity and river disconnecting. The status of water environmental degradation in this paper was analyzed based on the data and field investigation. The results indicated that the surface water area in the region has obviously decreased owing to the climate changes and human irrational use of water resources and the continuous lowering of the regional groundwater table and the steadily decreasing tendency of the flow rate in the source areas of the Yellow River.

Neutron activation analysis (NAA) and geochemical studies of 38 elements in surface sediments from lower reach and estuary of Huanghe (Yellow) River

Using a neutron activation analysis technique, which involves gamma-spectrometry with a Ge(Li) detector coupled to a S40 multichannel analyzer and interfaced to a PDP-11 computer, we determined thirty-eight elements in sediments from the lower reach (downstream from Jinan) and estuary of Huanghe. The results are discussed in this paper.From inter-elemental correlations, it ts found that a large number of metals (Mn.As, Co, Cr.Cs, Rb, Sc, Ti, Ta, V and Zn) correlate positively with Fe. Ba and Ca correlate positively with Al. Whereas some elements (e. g. , Ti and lanthanides) show no correlation with either Fe or Al. On the other hand, Hf and Zr show a negative correlation with Fe. Elements which tend to be scavenged by Fe and Al colloids or suspended particles are enriched in sediments at the Huanghe Estuary relative to its lower reach. On the other hand, the contents of some elements (e. g. , Zr,Hf,U, Ba, etc. )are higher in sediments from the lower reach of Huanghe than in the estuarine sediments,which may be related to the sorting during deposition of source materials. On the basis of their chemical property and geochemical behavior, the 38 elements we studied are classified into seven groups. (1) weathering-prone elements,group A:K,Rb, Cs and Na; (2) weathering-prone elements, group B:Mg, Ca, Ba and Al; (3) transition elements:Fe, Co.Ni, Zn, As, Sb, Mn, Cr, W,Mo,V, Ta and Sc; (4) rare elements:group A (Zr and Hf) and group B (Ti); (5) rare earth elements:the lanthanides; (6) halogens: Cl and Br; amd (7) natural radioactive elements:U and Th. The basis for this classification is discussed and we emphasize that geochemical associations of elements in the natural environment are not necessarily in accord with their chemical properties as dictated by position at the periodic table.

Variation of precipitation for the last 300 years over the middle and lower reaches of the Yellow River

The precipitation at 17 stations over the middle and lower reaches of the Yellow River is reconstructed during the period of 1736―1910, using the snow and rainfall records in the Qing Dynasty, together with the instrumental observation data of precipitation and farmland soil moisture content. The soil physics model related to rainfall infiltration and the surface water bal-ance equation are taken as main reconstruction methodology. The field infiltration experiment by artificial rainfall is conducted to check the reliability. And the precipitation series over the middle and lower reaches of the Yellow River and its 4 sub-regions are established, going back to 1736. Analysis of the time series indicates that the abrupt change of precipitation from high to low oc-curs around 1915 over the middle and lower reaches of the Yellow River. During the three peri-ods of 1791―1805, 1816―1830 and 1886―1895, the precipitation is markedly higher than the mean of the series. While both the periods of 1916―1945 and 1981―2000 are characterized by less precipitation. Three periodicities of 22―25a, 3.9a and 2.7a are shown in the precipitation fluctuation over the middle and lower reaches of the Yellow River. Moreover, the periodical signal of 22―25a becomes weaker and weaker since the abrupt change of 1915 and disappears in the late 1940s, and then the periodical signal of 35―40a appears instead.

Reconstruction of cultivated land during mJid- Holocene in the middle and lower reaches of Yellow River and human impact on vegetations

Yangshao culture is the most important mid-Holocene Neolithic culture in the Yellow River catchment, and thus, a study on the impact of human activities on the environment is important. In the current study, the distribution pattern of the cultivated land in late Yangshao culture is reconstructed using GIS tool and site domain analysis （SDA）. The results show that the cultivated land during 5.5-5.0 ka BP was mainly distributed in the Weihe River valley, Luohe River valley, northwestern Henan Plain, Fenhe River valley and eastern Gansu region, especially concentrated in the Xi＇an-Baoji line of the Weihe River valley. At that time, at least 37,000 km2 of lands were reclaimed in the middle and lower reaches of the Yellow River, and 132,000 km2 of lands were affected by agricultural activities. Human activities had become the driving force of land use/land coverage. Charcoal records indicate that the ancestors of Yangshao culture burnt forests for reclamation, leading to the decrease of arbor pollen at 5 ka BP in core areas of the Yangshao culture. The areas that were significantly affected by human activities accounted for 3.2% of the Yangshao culture influenced area, while the moderately affected areas accounted for 20.1% of Yangshao culture influenced area. Meanwhile, 92% of the land areas on the edge and outside of the Yangshao culture influenced area were not affected by human activities. The arbor pollen in these areas did not decrease until 4.0 ka BP.

Study on the groundwater exploitation test in the Yellow River lower reaches——Acase studyon the north suburb waterworks of Zhengzhou,China

This paper presents the studies on groundwater resources potential of the Yellow River (YR) terrace in Zhengzhou area, China. The main aim of the research was to resolve water shortage problems induced by recent but frequent drying ups of the YR in its lower reaches. Geologic explorations and grouped-pumping tests were conducted in the area. Based on collected data a groundwater flow net was established. The buried depth of groundwater level and water bearing potential of the aquifers were evaluated. Conventional method was used to determine recharge of the groundwater by lateral infiltration of the YR in pumping patterns. The results show that the study region has a high water bearing potential and offers conditions for the construction of large water works. However, only limited recharge by lateral infiltration from the river is available when developing large scale groundwater exploitation in the riverside of the YR. Environmental impacts induced by embankment stability of the Great dyke of the YR could be minimized or eliminated by appropriate engineering methods.

An analysis of soil composition and mechanical properties of riverbanks in a braided reach of the Lower Yellow River

The channel adjustment in a braided reach is very prominent in the fluvial processes of the Lower Yel-low River, in which the process of bank erosion plays an important role, especially during the period of clear water scouring. The process of bank erosion is closely related to soil composition and mechani-cal properties of the riverbanks. In this paper, the recent bank erosion process in a braided reach be-tween Huayuankou and Gaocun was firstly investigated after the water impoundment and sediment detention of the Xiaolangdi Reservoir, and then a field observation and indoor soil tests were con-ducted at 10 typical riverbanks in the braided reach. Through analyzing the experimental results, changes of riverbank-soil composition and mechanical properties were found, and the two real reasons causing serious bank erosion in the braided reach were identified. The following conclusions were drawn from this study: (i) the majority of riverbanks are made up of cohesive soil, and can be charac-terized by obvious vertical stratification structures of soil composition; (ii) these riverbanks are very erodible due to the lower clay-content and weak erosion-resistant strength in the bank soil, with its critical shear stress value (0.1―0.3 Pa) being much less than that of the average near-bank flow shear stress (2.0―3.0 Pa), which is one important reason causing serious bank erosion; (iii) frequent occur-rence of bank failure during flood seasons usually results from the fact that the values of shear strength parameters such as the cohesion and internal friction angle decrease with the increase of water content in riverbank soil, and the value of cohesion reduces drastically from 34 to 4 kPa with the increase of water content, which is another important reason causing serious bank erosion in the braided reach.

小浪底水库运行以来对黄河下游河道河床演变特性的影响

小浪底水库自1999年10月下闸蓄水,23年来深刻改变了进入黄河下游河道的径流泥沙过程,进而引起了下游河道的再造床。本研究以1960—2022年长序列水文泥沙、断面地形、遥感影像等多源资料为基础,从径流泥沙、冲淤演变、形态调整三个方面阐明了小浪底水库运行以来对下游河道河床演变特性的影响。结果表明:(1)水库拦沙效果显著,下泄水量在年内分配更加均匀、沙量则向汛期更加集中;大流量和高含沙事件的严重程度和发生频率均有所降低;悬沙调整不明显,床沙粗化显著。(2)扭转了黄河下游河道持续淤积的趋势,冲淤调整主要发生在花园口至高村的游荡性河段;冲刷效率持续下降,主槽过流能力得到显著恢复。(3)游荡性河段横断面形态向窄深发展,二级悬河发育得到有效缓解,整体河势处于相对稳定状态。研究成果丰富了多沙河流修建水库对下游河道影响的科学认识,也可为小浪底水库优化调度提供科技支撑。

黄河中下游过渡区河岸植物多样性与土壤因子的关系

[目的]河岸带物种多样性与土壤因子的关系对维持河岸带生态系统的稳定性十分重要,为揭示黄河中下游河岸带物种多样性与土壤因子的关系,进一步为黄河中下游过渡区河岸生态恢复、保护和高质量发展提供一定的参考与理论指导。[方法]采用样方调查法、试验分析法、CCA排序法等方法,以河南黄河中下游过渡区对植物分布和物种多样性与土壤因子的关系进行研究。[结果](1)黄河中下游过渡区河岸有机质、速效钾及有效磷均属于中等变异程度,土壤含水量、全氮变异系数为强变异性,土壤养分空间分布总体呈现中度不均匀的特征。(2)黄河中下游过渡区河岸植物优势度指数(D)与土壤全氮具有显著负相关关系(P<0.05);土壤pH值、速效钾和有效磷对物种丰富度指数(S)的影响不明显;均匀度指数(E)、香农-威纳指数(H)与6个土壤因子之间均没有达到显著水平。(3)红蓼、头状穗莎草、长芒稗、糠稷、醴肠群落的分布受土壤含水量的影响较大;青蒿、酸枣、毛白杨等的分布主要受全氮的影响较大,在全氮含量较高的区域分布较多;葎草和反枝苋受速效钾影响较大;而狗牙根、苍耳、芦苇、狗尾草、春蓼、绿豆等群落受土壤因子的影响较小。[结论]黄河中下游过渡区河岸带土壤含水量、速效钾及全氮是影响植物分布的主要因子,不同植物对土壤条件的需求存在差异,能够直观反映出植被与土壤环境之间的关系。

初论黄河下游河道的河槽线

黄河白鹤镇至陶城铺河段两岸堤距宽,历史上河道冲淤变化迅速、河势游荡多变,经多年河道整治,总体上河势得到基本控制,滩槽逐步稳定。在此条件下,为促进黄河的生态保护和滩区发展,提高河道管理水平,将河道粗分为河槽与滩地,首次提出河槽线的概念,明确了河槽线的含义及绘制河槽线的原则,强调绘制河槽线要以防洪安全为前提,给出了河槽线的绘制方法及其现场标示办法,分析了河槽线的作用等。

长江中下游及邻区地震各向异性对区域构造演化的启示

大别山东缘和长江中下游地区是我国东部构造格局最复杂的地区之一.为深入理解和认识该区的构造演化过程和壳幔变形特征,本文利用NW-SE向跨越长江中下游地区的密集宽频带流动地震台站数据,开展了远震接收函数Pms各向异性研究,并结合已有研究进一步分析了该区地壳与上地幔各向异性特征及其产生机制.结果表明:长江中下游及邻区地壳各向异性呈明显的横向分区性,华北克拉通东南部以近NWW向为主,而长江中下游和华南东北部以NE向为主.在垂向上,该区地壳与上地幔各向异性方向也存在明显差异,Pms各向异性快波方向与XKS(PKS,SKS,SKKS)快波偏振方向整体上存在30°~60°左右差异,形成了该区壳幔各向异性的“立交桥”式分层结构.本研究认为印支期和燕山期的区域构造演化差异以及华北与华南块体的流变学强度不同是造成该区壳幔各向异性“立交桥”式分层结构的重要因素.华北地区Pms各向异性特征反映了华南与华北块体在印支期陆陆碰撞所形成的中下地壳变形痕迹,华南东北部地区的Pms各向异性则主要受控于燕山期古太平洋板块俯冲造成的陆内挤压作用.燕山期古太平洋板块的北西向俯冲作用不仅导致了软流圈物质沿NW或近W向流动和橄榄岩矿物晶体的定向排列,也在地壳和岩石圈尺度产生了陆内挤压作用并最终导致了目前观测到的中下地壳变形和各向异性特征.

河南黄河中游、下游湿地优势草本植物生态位与种间联结性研究

本研究以河南黄河中游及下游湿地为研究区,对区内19种优势草本植物的生态位与种间联结性进行分析,以期对黄河中游、下游湿地的生态恢复和科学治理提供依据。结果显示,研究区共调查到116种草本植物,其中19种优势草本植物种间生态位差异较大。黄河中游、下游湿地总体联结性呈显著正联结;黄河中游和下游AC值≥0.4的均为2对,优势种种间联结性较弱,物种独立性较强。研究结果表明,黄河湿地植物群落总体呈现正向演替,但这种演替不稳定,还处于初级阶段。在生态修复过程中可以优先考虑具有较高生态位宽度且适应性强的植物,如芦苇(Phragmites australis(Cav.)Trin.ex Steud.)、香附子(Cyperus rotundus L.)作为先锋植物以加快演替进程。

黄河下游近期持续冲刷过程中床沙粗化特性分析

床沙组成的变化影响悬沙沿程恢复及河床阻力变化。本文基于黄河下游7个水文站1999—2020年的实测床沙资料,计算了各水文断面不同粒径组床沙占比的年际变化,分析了近二十年持续冲刷过程中不同河型河段床沙的时空粗化特性,讨论了河床冲淤过程对床沙粗化的影响。从时间来看,小浪底水库运用后,不同时期床沙的粗化特点不同,拦沙初期(2000—2006年)急剧粗化,拦沙后期(2007—2020年)粗化放缓,高村站及上游各站床沙呈波动粗化,高村站以下则变化不大,且粗化程度最强处由游荡段向下游过渡段转移;从空间来看,床沙沿程细化,游荡段以极粗沙为主,过渡段以粗沙和极粗沙为主,弯曲段的中细沙不可忽视。拦沙初期各河段床沙组成的调整表现为中细均冲;拦沙后期则表现为中粗均冲,极粗沙占比增大,利津以上各站细沙占比不足5%,对悬沙的补给受限,中沙和粗沙仍经受冲刷,极粗沙对相应悬沙有较好补给作用。河段汛后床沙中值粒径与河床累计冲刷量呈良好的幂函数正相关关系,但拦沙后期床面已粗化到相当程度,河床冲淤对床沙粗化的影响受限。研究结果有助于掌握近期整个黄河下游床沙的粗化现状及预测下游河道冲淤变形规律。

黄河下游水资源承载力与粮食生产韧性时空耦合及驱动因素

[目的]探究黄河下游水资源承载力与粮食生产韧性协同发展水平,为推动水资源保护利用和粮食生产协调发展提供新的政策视角。[方法]基于水资源承载力和粮食生产韧性评价指标体系,采用熵权法测算2010—2021年黄河下游水资源承载力和粮食生产韧性指数,运用耦合协调度模型和核密度估计分析两者协调发展时空演变特征,同时借助地理探测器探究影响两者耦合协调度的主导因子和交互因子。[结果]时间维度上,水资源承载力与粮食生产韧性耦合协调度由0.484 0上升至0.747 6,耦合协调度类型由濒临失调上升至中级协同;空间维度上,两者耦合协调度最高值出现在山东省济南市,最低值集中在河南省境内;年降水量、居民生活用水量、城市绿地面积、耕地面积和财政支农力度5项因子是两者协调发展的主导驱动因子,各主导因子的交互作用解释力表现呈现为双因子增强或非线性增强的特征。[结论]黄河下游水资源承载力和粮食生产韧性耦合协调度逐年上升并逐渐呈现出“东高西低”的空间分布特征,同时两大系统发展日趋紧密,交互作用逐渐增强。

历史时期黄河下游地区古湖分布与消亡原因

基于黄河下游古湖历史文献资料,详细估测了历史时期黄河下游130余个古湖的大致形状和面积,对各古湖的消亡过程进行了详细的总结和分析,并进一步讨论了导致古湖消亡的原因。结果表明:(1)历史时期黄河下游地区至少有135个湖泊,总面积高达16195.64 km^(2),主要沿黄河古河道分布,其中中小型湖泊(面积小于等于100 km^(2))为黄河下游古湖的主体,分别占历史时期湖泊总数、总面积的74.81%、30.23%。(2)自宋朝以来黄河下游古湖整体呈萎缩消亡态势,中小型湖泊消亡数量最多,占历史时期湖泊总数的60.34%;现代仍存湖泊数量为28个,减少了79.26%,总面积4910.66 km^(2),减小了69.68%。(3)气候变化是古湖消亡的背景,黄河改道泛滥带来的泥沙淤积是促使古湖消亡的直接原因,而人类围湖造田等活动加速了这一进程。